The usage of medical imaging devices to diagnose and plan treatment for various internal ailments is well known. Often, an imaging device such as an X-ray device, Computer Tomography (CT), or Magnetic Resonance Imaging (MR) device is used to generate one or more initial scans or images of the area of interest. These initial scans may be acquired by focusing a beam of radiation into a target volume and collecting the traversing beams in an imager. The beams collected by the imagers are used to generate a display (i.e., one or more images) of the targeted volume that may be used to diagnose or monitor an afflicted area (e.g., a tumor or lesion or a surrounding area).
Typically, once an image has been acquired, critical structures (e.g., regions or organs) disposed in the target area must be specifically identified so that treatment may be optimally directed. Conventional medical imaging techniques include techniques for automatically identifying (“segmenting”) organs and large structures. These techniques often include delineating adjacent structures by derived radiodensities and classifying the structures according to their relative positions and derived densities with known values. However, even with automatic segmentation of anatomical structures, identification of these regions often also includes tracing the outline (“contouring”) of these or other structures. For example, radiation targeting a specific organ or a portion of an organ may require specific identification and/or demarcation of the portion(s) of the organ to receive treatment. Likewise, tumors can also be specifically contoured and identified for treatment. For certain treatment plans, it may be preferred to designate these identified portions by specifically contouring the circumference of the area.
Traditionally, this contouring has been performed manually and this process is performed at least once on a diagnostic planning CT, with the generated structures subsequently being used for calculation of the treatment plan. Newer technology and advanced techniques allow for improved image collection through the use of a cone-beam computerized tomography system (CBCT). In conventional computerized tomography systems, one or more 2D slices are reconstructed from one dimensional projections of the patient, and these slices may be combined to form a three dimensional (3D) image of the patient. A cone beam computerized tomography system is similar to that of a conventional computerized tomography system, with the exception that an entire volumetric image is acquired through rotation of the source and imager, and a fully 3D image is reconstructed from a plurality of 2D projections. Unfortunately, manually drawing the individual contours on a contiguous set of 2D slices then combining them for each image of an entire data set can be extremely time consuming and labor intensive. The time and labor increases even more with the number of image slices and the number and respective sizes of the anatomical structures (e.g., organs, tumors, etc.) in the particular area of interest.
Moreover, specific anatomies may change (sometimes drastically) over time and/or as a result of receiving radiation treatment over the course of a treatment plan. Specifically, the target volumes may expand or reduce in size, depending on the ailment and the efficacy of the treatment plan. As such, treatment plans designed around diagnostic images generated during an initial CT scan may be ineffective, inefficient, or even dangerous to treat patients. In order to ensure optimal targeting and positioning, updated images of the treated area are sometimes acquired periodically by generating additional images during the treatment process to ensure an appropriate positioning of the therapeutic radiation beam and to determine the effectiveness of the treatment regimen. Recently developed treatment machines allow for the detection of anatomical changes by employing advanced imaging acquisition techniques such as cone-beam computer tomography (CBCT) at the site of the treatment machine, often either immediately before or after treatment is administered to the patient.
While the timing of the updated image generation and treatment may differ according to the particular patient and/or treatment plan, some treatment plans include monitoring by acquiring monitoring images on a daily basis. Unfortunately, reliance on updated images also increases the contouring workload, particularly if the data is used for plan adaptation since any additional contouring that was manually performed is typically not preserved over additional image generation and through the application of conventional automatic segmentation techniques. Due to its sensitive nature, manual contouring of and within anatomical structures for treatment purposes can be very time consuming. As such, manually replicating contouring for a multitude of images can be an extremely intensive and inefficient process.